Methods for determining past nutritional intake are essential for investigating possible dietary risk factors for cancer. In order to assess the accuracy and validity of such methods, nutrient data from the past are needed to compare with current recall of that same time period. A subgroup of participants from the Chicago Coronary Prevention Evaluation Program (CPEP) from whom periodic dietary data were collected from 7-day food records during 1958-1969 have consented to participate in this study. Their ability to recall their nutritional intake at the time of the original study as well as the ability of their spouse or other surrogate t provide that information will be tested in two ways. Diet history questionnaires will be mailed and completed independently by participants and surrogates. Upon completion of the questionnaire, detailed nutrition interviews will be conducted by trained nutritionists. Dietary information collected by each of these methods wil be converted to nutrient intakes based on the CPEP coding system used in the original dietary analyses for comparison to the original nutrient intakes. In addition, the original dietary data will be adapted to a format comparable to those of the questionnaire and the diet history interview to provide complete nutrient analyses. A second cohort of participants recruited from a long term prospective study conducted during 1958-1959 in the Chicago Peoples Gas Study will also be asked to provide dietary recall information using the identical dietary history interview form that was initially employed. Use of this population-based cohort offers a means for comparison of recall ability with the CPEP cohort which was selected on the basis of health status. Data analyses will include tests for accuracy and reliability of the long term dietary recall questionnaire and interview. Also, tests to evaluate feasibility of these two methods will be included. Results from analyses to test accuracy will be employed to compare whether active participation in a dietary intervention study by the CPEP cohort may have influenced recall ability.